On 2013-08-21 2:00 PM, Natanael wrote:
Well, the point here is that ZRTP for video and voice pretty much is
functionally equivalent to OTR for IM. OTR is designed for messages,
ZRTP is designed for data streams.
Ah yes, I see:
I was thinking of the problem from a text point of view, where
cryptographically identifying the right target is hard. In video, not hard.
*ZRTP] allows the detection of man-in-the-middle (MiTM) attacks by
displaying a short authentication string (SAS) for the users to read
and verbally compare over the phone**.* ... But even if the users
are too lazy to bother with short authentication strings, we still
get reasonable authentication against a MiTM attack, based on a form
of key continuity. *It does this by caching some key material to use
in the next call, to be mixed in with the next call's DH shared
secret, giving it key continuity properties analogous to Secure
SHell (SSH)*.
If you know the face of the person you are talking to, you can surely
tell if the right person is speaking the right SAS, which makes the
methods used by OTR overkill for video.
Since humans are good at live face recognition, this makes it possible
to locate the target person by insecure identifiers.
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